US6814409B2 - Hydraulic drive system - Google Patents

Hydraulic drive system Download PDF

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US6814409B2
US6814409B2 US10/121,266 US12126602A US6814409B2 US 6814409 B2 US6814409 B2 US 6814409B2 US 12126602 A US12126602 A US 12126602A US 6814409 B2 US6814409 B2 US 6814409B2
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fluid
pump
valve
circuit
chamber
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US10/121,266
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US20020149248A1 (en
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Henry Warn Jackson
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A Dec Inc
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A Dec Inc
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Assigned to A-DEC, INC. reassignment A-DEC, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: JACKSON, HENRY WARN
Priority to JP2002265383A priority patent/JP4172974B2/ja
Priority to EP02020775A priority patent/EP1353076B1/de
Priority to DE60231287T priority patent/DE60231287D1/de
Priority to AT02020775T priority patent/ATE423912T1/de
Publication of US20020149248A1 publication Critical patent/US20020149248A1/en
Publication of US6814409B2 publication Critical patent/US6814409B2/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61G—TRANSPORT, PERSONAL CONVEYANCES, OR ACCOMMODATION SPECIALLY ADAPTED FOR PATIENTS OR DISABLED PERSONS; OPERATING TABLES OR CHAIRS; CHAIRS FOR DENTISTRY; FUNERAL DEVICES
    • A61G15/00—Operating chairs; Dental chairs; Accessories specially adapted therefor, e.g. work stands
    • A61G15/02—Chairs with means to adjust position of patient; Controls therefor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/04—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
    • F15B11/046—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed depending on the position of the working member
    • F15B11/048—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed depending on the position of the working member with deceleration control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B7/00—Systems in which the movement produced is definitely related to the output of a volumetric pump; Telemotors
    • F15B7/005—With rotary or crank input
    • F15B7/006—Rotary pump input
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B7/00—Systems in which the movement produced is definitely related to the output of a volumetric pump; Telemotors
    • F15B7/02—Systems with continuously-operating input and output apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/20507—Type of prime mover
    • F15B2211/20515—Electric motor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20561—Type of pump reversible
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/27—Directional control by means of the pressure source
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30525—Directional control valves, e.g. 4/3-directional control valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/315—Directional control characterised by the connections of the valve or valves in the circuit
    • F15B2211/31552—Directional control characterised by the connections of the valve or valves in the circuit being connected to an output member and a return line
    • F15B2211/31558—Directional control characterised by the connections of the valve or valves in the circuit being connected to an output member and a return line having a single output member
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/327—Directional control characterised by the type of actuation electrically or electronically
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • F15B2211/40507—Flow control characterised by the type of flow control means or valve with constant throttles or orifices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • F15B2211/40515—Flow control characterised by the type of flow control means or valve with variable throttles or orifices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/415—Flow control characterised by the connections of the flow control means in the circuit
    • F15B2211/41527—Flow control characterised by the connections of the flow control means in the circuit being connected to an output member and a directional control valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/415—Flow control characterised by the connections of the flow control means in the circuit
    • F15B2211/41581—Flow control characterised by the connections of the flow control means in the circuit being connected to an output member and a return line
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/42—Flow control characterised by the type of actuation
    • F15B2211/428—Flow control characterised by the type of actuation actuated by fluid pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/46—Control of flow in the return line, i.e. meter-out control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/61—Secondary circuits
    • F15B2211/613—Feeding circuits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/615—Filtering means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/625—Accumulators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7052—Single-acting output members
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/80—Other types of control related to particular problems or conditions
    • F15B2211/85—Control during special operating conditions
    • F15B2211/851—Control during special operating conditions during starting
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/80—Other types of control related to particular problems or conditions
    • F15B2211/85—Control during special operating conditions
    • F15B2211/853—Control during special operating conditions during stopping

Definitions

  • This invention relates generally to a hydraulic drive system and elements thereof which may be used for actuating devices having multiple operations, such as a chair having both lift and tilt features.
  • Hydraulic drive systems are used in many operations for powering multiple actions. Examples of such are power actuated chairs, such as dental chairs, which often are operated by pressurized hydraulic fluid systems in which one hydraulic cylinder, or ram, is operable to raise the chair, and a second hydraulic cylinder, or ram, is operable to tilt the chair or a portion thereof. Many prior hydraulic drive systems have been disclosed in the past, but each has had disadvantages.
  • prior systems use drive pumps, motor units, and control circuits which produce movement of the item to be driven in a manner which is not as smooth as may be desired.
  • prior systems may produce movement which is too fast, too slow, or may produce jerking start and stop actuation which is uncomfortable for the user.
  • Prior systems also have been constructed in such a manner that they are more complex and expensive than may be desired to fulfill their functions. Often prior systems have been produced in such a manner that they require an undesirable number of actuating valves and are produced in a generally open architecture of hoses and connections which are subject to breakage and leakage.
  • An object of the present disclosure is to provide a novel, efficient, and economically produced hydraulic drive system.
  • Another object is to provide a hydraulic drive system which produces smooth operation of driven components actuated by the system.
  • an object is to provide a hydraulic drive system such as is used to drive raising and tilting cylinders for a chair, such as a dental chair, in such a manner as to provide comfortable starting, stopping, and intermediate operation for a party carried in the chair.
  • Another object is to provide a system in which a bi-directional crescent gear pump drive is used to provide a substantially pulseless supply of pressurized fluid, with actuation of the pump in one direction providing pressurized fluid to one ram in the system, and actuation of the pump in the opposite direction providing pressurized fluid to the other ram in the system.
  • an electric drive motor for the pump may be used which is capable of producing greater torque in one direction than in the reverse direction, such that it may drive the pump in the direction of greater torque output to produce lifting of the chair, and may drive the pump in the reverse, lower powered, direction of the motor for producing tilting.
  • a still further object of the present disclosure is to provide a novel hydraulic drive system in which a minimum number of hydraulic circuit control components are required.
  • Yet another object is to provide a novel hydraulic drive system in which a monolithic body has a plurality of bores formed therein which extend inwardly from external surface regions of the body but do not extend fully through the body, with selected ones of the plurality of bores intersecting to produce desired fluid flow channels in a fluid supply and a fluid return circuit in the system.
  • a system with such a monolithic body may be produced with a minimum number of machining operations for economy in manufacture and minimizes fluid leakage.
  • a further object of the disclosure is to provide valve assemblies for controlling fluid flow in the system, which valve assemblies are operatively mounted in selected one of said bores in the monolithic body.
  • Yet another object is to provide a novel cushion valve in a fluid control system which produces cushioned starting of fluid flow to moderate acceleration during actuation.
  • Another object is to provide a novel self-actuating fluid flow rate control valve in a pressurized fluid system operable to advantageously control the rate of fluid flow in the system throughout a wide range of operating conditions.
  • FIG. 1 is a side elevation view of a hydraulically actuated chair having lift and tilt mechanism operable by a hydraulic drive system according to an embodiment of the present invention
  • FIG. 2 is a schematic diagram of a hydraulic drive system incorporating features according to the present invention
  • FIG. 3 is a top perspective view of a major portion of a hydraulic drive system according to the present invention.
  • FIG. 4 is an exploded perspective view of several of the component parts of the system illustrated in FIG. 3;
  • FIG. 5 is a bottom perspective view of a manifold block in the system with gear pump and check valve assembly components ready for installation;
  • FIG. 6 is a top perspective view of the manifold block alone
  • FIG. 7 is a top plan view of the manifold block
  • FIG. 8 is an end view of the manifold block taken along line 8 — 8 in FIG. 7;
  • FIG. 9 is a bottom plan view of the manifold block
  • FIG. 10 is a cross sectional view taken along the line 10 — 10 in FIG. 7;
  • FIG. 11 is a cross sectional view taken along the line 11 — 11 in FIG. 7, with a motor, gear pump, and fluid sump attached;
  • FIG. 12 is a cross sectional view taken along the line 12 — 12 in FIG. 7 with a pair of solenoid actuated valves secured to the manifold block;
  • FIG. 13 is an enlarged cross sectional view taken generally along the line 13 — 13 in FIG. 8 with various valve assemblies in bores in the manifold;
  • FIG. 14 is an enlarged cross sectional view taken generally along the line 14 — 14 in FIG. 8 with cushion valve assemblies received in bores in the manifold;
  • FIG. 14A is an enlarged view taken along the line 14 A— 14 A in FIG. 14;
  • FIG. 14B is a view taken along the line 14 B— 14 B in FIG. 14A;
  • FIG. 15 is an enlarged cross sectional view taken generally along the line 15 — 15 in FIG. 7 with check valve assemblies in bores in the manifold and a fluid sump secured thereto;
  • FIG. 16 is an enlarged cross sectional view taken generally along the lines 16 — 16 in FIG. 7 with flow rate control valve assemblies received in bores in the manifold block;
  • FIG. 17 is an enlarged view of one of the solenoid valve assemblies illustrated in FIG. 12 with an adapter through which it is connected to the manifold block;
  • FIG. 18 is a side elevation view of the adapter of FIG. 17;
  • FIG. 19 is a top plan view of the adapter.
  • FIG. 20 is a bottom plan view of the adapter removed from the assembly.
  • FIG. 1 one manner of use of a hydraulic drive system according to the invention is illustrated for use with a dental chair 10 .
  • the chair has a base 12 adapted to rest on a floor 14 with an upper structure including a seat portion 16 and a back, or back rest, 18 .
  • the seat is mounted on a lift mechanism 20 which includes an extensible contractible ram, or cylinder, 22 . Extension of the ram acts to raise the chair to the elevated position illustrated in solid outline in FIG. 1 . Contraction of the ram lowers the chair to the position illustrated in dashed outline at 10 a in FIG. 1 .
  • the chair back 18 is pivotally connected to the rear end of seat 16 and tilting mechanism including a tilt ram, or cylinder, 24 is operable to tilt the seat and back between a generally upright position illustrated in solid outline in FIG. 1 and a rearwardly tilted position illustrated at 10 b in dashed outline.
  • tilting mechanism including a tilt ram, or cylinder, 24 is operable to tilt the seat and back between a generally upright position illustrated in solid outline in FIG. 1 and a rearwardly tilted position illustrated at 10 b in dashed outline.
  • a hydraulic drive system for the lift and tilt cylinders is illustrated generally at 28 in a broken away portion of base 12 .
  • the drive system 28 includes a fluid supply tank, or reservoir, 30 for supplying hydraulic operating fluid to the primary drive unit which includes a motor and pump combination 32 .
  • the fluid in the supply tank is retained at a level above the top of a base manifold 36 , described below.
  • the motor/pump combination 32 generally includes a base manifold 36 (also referred to herein as “base” or “manifold”) atop which is mounted a reversible, or bi-directional, electric motor 38 .
  • the motor used in the embodiment described is an AC motor, but others may be used also.
  • a crescent gear pump assembly 42 is connected to the bottom of base 36 with the shaft 110 of electric motor 38 extending downwardly through the base to drive pump 42 . The component parts of the gear pump and their assembly will be described in greater detail below.
  • a fluid holding sump, or reservoir, 44 underlies the base and may be filled with hydraulic fluid from reservoir 30 to be pumped therefrom by pump 42 and distributed to operating cylinders, or rams, such as lift ram 22 and tilt ram 24 such as would be used for actuating the powered lift and/or tilt mechanism of a chair.
  • the motor being bi-directional may be capable of supplying greater power, or torque, when operated in one direction than in the opposite direction.
  • the motor/pump combination preferably will be connected in the system, such that it will operate in its mode of greatest power, or torque to supply chair lifting energy.
  • FIG. 2 A simplified hydraulic schematic diagram for the system is shown in FIG. 2 .
  • Lift, or first, cylinder, or ram, 22 is shown which may be used to lift a chair upon pressurized fluid being introduced to the lower end of the ram.
  • a tilt, or second, cylinder, or ram, 24 is provided for tilting the chair fore and aft. Introducing pressurized fluid to the lower end of the tilt cylinder causes it to tilt the chair in one direction and a spring and gravity may be utilized upon release of such fluid to return the cylinder to a retracted condition.
  • the system, in addition to cylinders 22 , 24 includes the previously described bi-directional electric motor 38 , pump 42 , and fluid holding sump 44 .
  • the system also includes a pair of solenoid actuated valves 48 , 50 , flow rate control valves 54 , 56 , cushion valve assemblies 60 , 62 , and one-way check valves 64 , 66 , 68 , 70 .
  • the system also includes a pair of hydraulic accumulators 74 , 76 and pressure relief valves indicated generally at 80 , 82 .
  • An operator's touch pad, or foot switch, 86 is provided which is operatively coupled to a circuit board 88 for controlling actuation of motor 38 and solenoids 48 , 50 to produce desired actuation of the lift and tilt cylinders as will be described in greater detail below.
  • a plurality of filters 84 are disposed in the circuit to remove contaminants and maintain cleanliness of hydraulic fluid in the system.
  • motor 38 is operated in one direction to operate pump 42 , such that hydraulic fluid is drawn from sump 44 through check valve 64 , is pumped through pump 42 to increase its pressure, and is pumped out through check valve 70 , accumulator 76 , and flow-rate control valve 56 , to the lower side, or end, of ram 22 , thus extending the ram.
  • Check valves 66 , 68 remain closed. These components and appropriate connectors form a fluid supply circuit for the lift cylinder.
  • motor 38 is operated in the opposite direction causing pump 42 to turn in the opposite direction to draw fluid from sump 44 through check valve 68 through pump 42 , and distribute it under pressure through check valve 66 , accumulator 74 , and flow rate control valve 54 to the tilt cylinder 24 .
  • Check valves 64 , 70 remain closed.
  • solenoid valves 48 , 50 are in the positions illustrated with flow prohibited through these valves, thus preventing return of fluid to the reservoir from either of the cylinders 22 , 24 .
  • solenoid 50 is actuated, such that flow is allowed therethrough in the direction of arrow 50 a .
  • the weight of the chair (and also of a person therein if occupied) causes fluid to flow from the ram through fluid flow rate control valve 56 , accumulator 76 , solenoid valve 50 , and through cushion valve assembly 62 to return fluid to sump 44 .
  • These components and appropriate connectors form a fluid return circuit for the lift cylinder.
  • solenoid valve 48 is actuated so that fluid may flow therethrough in the direction of arrow 48 a , through a flow rate control valve 54 , accumulator 74 , solenoid valve 48 , and through cushion valve assembly 60 to return to sump 44 .
  • These components and appropriate connectors form a fluid return circuit for the tilt cylinder.
  • a spring, or gravity, and the weight of a person, if occupied, operating on the tilt cylinder causes fluid to flow therefrom when solenoid valve 48 is opened.
  • Dashed lines 94 , 98 illustrate fluid return lines through which fluid which may leak past seals in the operating components to which they are connected may return freely to the sump and for the transport of air from the rod end of the rams on extension of the rams.
  • Line 96 vents the electric motor shaft seal from overpressurization.
  • Lines 92 , 100 connect the lower-pressure sides of accumulators 74 , 76 to sump 44 , as will be described in greater detail below.
  • Control orifices 93 , 101 are indicated in lines 92 , 100 , respectively, through which fluid from the lower pressure side of accumulators 74 , 76 may return to sump 44 .
  • manifold 36 is shown as a monolithic, or unitary, block having a plurality of bores and other openings machined therein.
  • the base, or manifold, block 36 has a motor receiving cavity 104 formed in its upper side into which motor 38 fits as illustrated generally in FIG. 11 .
  • the motor includes a stator 106 , and a rotor 108 which has an elongate rotor, or drive, shaft 110 depending therefrom.
  • a shaft seal 112 is provided to fit about shaft 110 on installation.
  • the manifold body has a bore 114 extending vertically therethrough through which shaft 110 extends.
  • the lower end of shaft 110 opens into a shallow cylindrical bore, or cavity, 118 formed in the bottom of the manifold block 36 adapted to receive components of the pump assembly.
  • shallow bore 118 and motor shaft bore 114 which opens thereinto are non-concentric, with their center axes being offset. This is to accommodate the gear pump assembly 42 as will be described in greater detail below.
  • kidney-shaped openings 120 , 122 are formed, or machined, in the top of cavity 118 and extend a short distance upwardly into the manifold block 36 from cavity 118 .
  • the kidney-shaped openings are referred to as back tilt gear feed kidney and base lift gear feed kidneys, respectively, and are symmetrically disposed on opposite sides of motor shaft bore 114 .
  • pump assembly 42 includes four primary components. These include a base plate 126 to which an upstanding separator crescent 128 is secured.
  • the crescent is substantially semi-circular in configuration having a concave inner side and a convex outer side.
  • a pinion drive gear 130 rests on base plate 126 and within the concave inner side of crescent 128 .
  • a driven ring gear 132 is positioned to extend about the convex outer side of crescent 128 and about pinion drive gear 130 and has inwardly facing gear teeth which mesh with outwardly directed teeth of drive gear 130 .
  • the base plate is bolted to the underside of manifold block 36 as best illustrated in FIG. 11, to produce a substantially tight fit therebetween, with crescent 128 , drive gear 130 , and ring gear 132 resting within cavity 118 .
  • Drive gear 130 is keyed to the lower end of drive shaft 110 to be driven thereby.
  • the assembled gear pump is positioned in cavity 118 underlying kidney-shaped openings 120 , 122 .
  • the inner drive gear 130 keyed to the motor drive shaft 110 is rotated in either of opposite directions by actuation of the bi-directional motor.
  • the teeth of the inner drive gear 130 mesh with the inwardly directed teeth of driven gear 132 and carry the driven gear with it upon rotation.
  • Hydraulic fluid is moved through the pump by the opening of cavities between the gear teeth at what might be considered an inlet side and meshing of the teeth on moving toward the discharge side.
  • the stationary crescent separates the suction and discharge portions of the pump.
  • Such a pump provides smooth and almost pulseless flow of fluid being pumped.
  • Describing manifold block 36 in greater detail, it has a plurality of substantially horizontally and longitudinally disposed bores 132 , 134 , 136 , 138 , 140 , 142 extending inwardly from one end of block 36 .
  • a side bore 144 extends laterally inwardly from a side of base 36 as best illustrated in FIGS. 4 and 5. It should be recognized that all of these horizontally extending bores 132 - 144 extend inwardly from their associated surfaces of the manifold block, but do not extend full therethrough to an opening at the opposite side of the block.
  • vertically extending bores 148 , 150 extend upwardly from kidney-shaped openings 120 , 122 , respectively, and intersect bores 136 , 138 , respectively.
  • a plurality of vertically extending bores 170 , 172 , 174 , 176 , 178 , 180 are formed in the lower, or under, side of block 36 . Again, these bores extend inwardly from their associated surface of manifold block 36 but do not extend fully through the manifold block to the opposite side thereof.
  • a plurality of vertically extending bores are provided in the bottom and top of the manifold block for receiving bolts or screws for holding the motor in place on the manifold block, and for bolting, or screwing, other assembly parts to the underside, or bottom, of the manifold block as will be described in greater detail below.
  • Fluid flow circuits within the manifold block are provided by intersections between selected ones of the horizontally disposed and vertically disposed bores.
  • kidney-shaped opening 120 intersects vertical bore 148 which intersects horizontal bore 136 .
  • kidney-shaped opening 122 intersects vertical bore 150 which intersects horizontal bore 138 .
  • bore 136 intersects vertical bore 160 and bore 138 intersects vertical bore 162 .
  • vertical bore 158 intersects horizontal bore 134 adjacent one end of block 36 , and at a more central portion of the block bore 134 intersects vertical bore 170 which opens to the bottom of the block.
  • vertical bore 164 intersects horizontal bore 140 which, at a more central portion of the block, intersects vertical bore 172 which opens to the bottom of the block.
  • horizontally disposed bore 132 intersects vertical bores 154 , 156 adjacent one end of the block, and at a more central region of the block bore 132 intersects horizontal infeed bore 144 and vertical bore 170 which opens to the bottom of the block.
  • horizontally disposed bore 142 adjacent one end of the block intersects vertical bores 166 , 168 and at a region more central of the block intersects vertical bore 178 which opens to the bottom of the block.
  • Each ball check valve includes a spring 184 , a ball 186 , and an elastomeric O-ring seal 188 .
  • One assembly including spring, ball, and O-ring is inserted into one of bores 176 , 178 and the other spring, ball and O-ring assembly is inserted in the other of such bores.
  • an additional relief 190 is machined in the mouth of each of the bores to receive its associated O-ring.
  • a cover plate 192 having a pair of fluid flow bores 194 , 196 extending therethrough is bolted to the underside of manifold block 36 using a plurality of screws, such as that indicated at 198 which extend through accommodating bores in plate 192 and are received in threaded bores on the underside of manifold block 36 .
  • the installed check valve assemblies are shown in FIG. 15 .
  • the circular, shallow pan, or sump, 44 is attached to the underside of the manifold block using a plurality of screws as indicated generally at 200 in FIG. 15 .
  • the sump pan has a large enough diameter that it encompasses bores 170 , 172 , 174 , 176 , 178 , 180 and cavity 118 . All of these bores opening to the bottom side of the manifold block therefore communicate with the sump.
  • Previously noted fluid supply reservoir, or tank, 30 is operatively connected to the assembly via a hose connection 202 (see FIG. 3) which allows hydraulic fluid to flow through bore 144 in one side of the manifold block into bore 132 and then to exit into sump pan 44 through bore 170 in the bottom of the block (see FIG. 13 ). Hydraulic fluid thus will flow freely into the sump pan 44 to be available for use in the system.
  • hydraulic fluid in fluid supply tank 30 is maintained at a level above the top of base manifold 36 . Fluid thus may be provided to and remain in at least portions of those bores and assemblies directly connected to sump 44 .
  • Fluid thus will generally fill motor shaft bore 114 to the level of shaft seal 112 to assure motor shaft lubrication.
  • a pair of hydraulic fittings 206 , 208 are screwed into the threaded outer end portions of bores 154 , 168 , respectively. These fittings provide connections for hydraulic tubes, or hoses, 210 , 212 which connect to the tilt cylinder and lift cylinder 24 , 22 , respectively.
  • a tilt cylinder check valve 66 mounted within bore 136 is a tilt cylinder check valve 66 , and a lift cylinder check valve 70 is mounted in bore 138 . Both of check valves 66 , 70 are similar in structure, and thus only one will be described in detail.
  • Each check valve ( 66 , 70 ) includes a cylindrical check valve seat member 216 which has a threaded exterior allowing it to be screwed into its associated bore which is internally threaded.
  • the seat member has a central bore 218 extending longitudinally therethrough.
  • the inner end region 218 a of bore 218 is hexagonal allowing the valve seat to be turned by a hex wrench to screw it into or remove it from its threaded connection in its associated bore.
  • the opposite end of bore 218 indicated at 218 b , has a larger cylindrical cross section.
  • a conically shaped valve seat 218 c extends between regions 218 a , 218 b of the bore.
  • a sealing assembly is mounted for shifting longitudinally in bore 218 relative to seat 218 c .
  • the sealing assembly includes an elongate stem 220 and an enlarged head 220 a .
  • An O-ring 222 is interposed between head 220 a and seat 218 c to produce sealing therebetween.
  • a check valve spring 224 yieldably urges the check valve assembly to a closed position as illustrated for check valve 70 with head 220 pressed tightly against O-ring 222 which bears against valve seat 218 c .
  • a threaded plug 226 screwed into the threaded outer end of bore 136 with an O-ring seal 228 therebetween seals the outer end of bore 136 and provides a stop for one end of spring 224 .
  • Pressure fluid entering through end portion 218 a of bore 218 acts against the check valve assembly to overcome the force of spring 224 and will open the valve to allow pressurized fluid to flow outwardly therethrough.
  • Pressure fluid impressed against the enlarged head 220 a on the spring side thereof acts to seal the check valve.
  • accumulators 74 , 76 are illustrated in greater detail. They are substantially similar in design, and thus only one will be described in detail. Referring to accumulator 76 , it includes a piston body, or plunger, 234 having a u-cup seal 236 extending thereabout. The piston body and seal are slidably mounted in bore 142 with a spring 238 yieldably biasing the piston body toward the outer end of bore 142 . A spring 239 in bore 132 associated with accumulator 74 is shorter than spring 238 and may exert a different biasing force.
  • pressure relief valve assembly 82 Mounted within piston body 234 is pressure relief valve assembly 82 .
  • a similar pressure relief valve assembly 80 is mounted in the piston body of accumulator 74 in bore 132 .
  • the pressure relief valve assembly 82 includes a check valve element 242 biased by a spring 244 toward a valve seat 246 with an O-ring 248 therebetween.
  • the spring forces exerted by springs 238 , 244 differ. Should a rapid increase in pressure beyond that which can be resisted by spring 244 be imposed upon the piston head the check valve element 242 will move away from seat 246 to allow the release of pressure fluid through piston body 234 to escape through bore 178 to the sump.
  • These component parts are illustrated generally slidably received in bore 142 with a screw plug 250 screwed into the threaded end of bore 142 with an O-ring seal 252 therebetween to seal the end of bore 142 and hold the component elements therein.
  • bores 170 , 178 could hold control orifices 93 , 100 , respectively, of a selected size to provide controlled return of fluid from bores 132 , 142 to sump 44 . Such controlled return of fluid could enhance the operation of the accumulators.
  • self-actuating flow rate control valves 54 , 56 are mounted in vertical bores 154 , 168 , respectively.
  • Each of the flow rate control valve assemblies 54 , 56 are similar, and thus only one will be described in detail.
  • An elongate cylindrical cup-shaped body 256 having a closed bottom end and an open upper end is received in bore 168 .
  • An O-ring seal 258 seals the space between body 256 and bore 168 . As is seen in the drawing, a major portion of the body 256 below O-ring seal 258 has a smaller diameter than bore 168 so that fluid may flow therepast.
  • a cylindrical spool 260 having a fluid control orifice 262 in its upper end is slidably mounted in close contact with the inner surface of body 256 .
  • Spool 260 is yieldably urged upwardly by a spring 264 against a retaining ring 266 .
  • a side bore 268 extends through at least one side of body 256 adjacent the lower end of spool 260 when the spool is resting against retaining ring 266 as shown in its position illustrated for assembly 56 .
  • the flow rate control valve assembly is inserted slidably into its associated bore 168 , as would be flow rate control assembly 54 in bore 154 , and then hydraulic fittings 206 , 208 are screwed into the threaded outer end portions of bores 154 , 156 serve to hold the flow rate control valve assemblies in their bores (see FIG. 3 ).
  • bore 168 is in fluid communication with horizontal bore 142 .
  • pressure fluid is supplied through bore 142 to bore 168 to direct operating fluid to a cylinder the assembly is in the position illustrated for assembly 56 .
  • Fluid flows from bore 142 into bore 168 through side bore 268 , up through spool 260 and through orifice 262 , with orifice 262 controlling the rate of fluid flow.
  • spool 260 After the initial excessive pressure surge, or flow rate, has subsided somewhat spool 260 will be urged slightly upwardly again to partially open side bore 268 and provide controlled flow rate through its upper orifice 262 .
  • the specified fluid flow rating is determined mainly by the diameter of control orifice 262 and the strength of spring 264 .
  • the tolerance of fit between body 256 and spool 260 , the length of spool 260 and the location and size of the side bore 268 also may have an effect on the function of this valve assembly.
  • cushion valve assemblies 60 , 62 are received in bores 134 , 140 , respectively. Since both of these cushion valve assemblies are substantially the same only one will be described in detail.
  • assembly 60 it includes an elongate, generally cylindrical, plunger, or element, 274 slidably mounted in bore 134 .
  • the closed end of plunger 274 is directed toward the outer end of bore 134 .
  • a hollow internal bore 276 extends through a major portion of the plunger and opens toward the opposite end of the plunger.
  • a spring 278 interposed between the closed inner end of bore 134 and plunger 274 yieldably biases the plunger 274 toward the outer end of bore 134 .
  • a check valve ball 280 is received within bore 276 between a conically-shaped valve seat 282 and a retainer sleeve 284 having an opening 284 a at its lower end.
  • Sleeve 284 is open at 284 b along one side thereof to allow passage of fluid past the sleeve.
  • Ball 280 is freely movable in bore 276 under the influence of fluid pressure imposed thereon between a closed position against valve seat 282 (as shown for assembly 62 ) and an open position spaced from valve seat 282 (as shown for assembly 60 ).
  • a cross bore 288 extends through a wall of plunger 274 forwardly of valve seat 282 .
  • Plunger 274 has the elongate, generally cylindrical, configuration illustrated in FIGS. 14, 14 A, and 14 B. Opposed sides of the forward end are beveled inwardly on progressing toward the forwardmost end as indicated at 274 a , 274 b . These beveled sides extend generally to the longitudinal midpoint of the plunger. The remainder of the forward portion of the plunger retains is generally cylindrical configuration between beveled sides 274 a , 274 b to provide good sliding contact and aligning engagement between the plunger 274 and its associated bore 134 throughout movement of the plunger in the bore. The beveled sides allow gradual opening of fluid flow passages from bore 34 to bore 170 as the plunger is shifted from its position as illustrated for cushion valve 62 to the position illustrated for cushion valve 60 .
  • Plunger 274 is not tightly confined, or sealed, against the walls of bore 134 and thus some fluid may seep therepast for purposes as will be described in greater detail below.
  • Cushion valve assemblies 60 , 62 are slidably mounted in their respective bores 134 , 140 adjacent intersecting bores 170 , 172 , respectively.
  • the cushion valve plungers are shiftable under the influence of pressure in their respective bores between a closing position as illustrated for cushion valve assembly 62 and an open flow position as illustrated for valve assembly 60 .
  • Plungers 274 each have a cross sectional configuration closely complementary to the cross sectional configuration of their associated bores 134 , 140 . In an at rest condition bores 134 , 140 , 170 , 172 are below the level of the hydraulic fluid held in supply tank 30 , and thus the components of the cushion valve assembly 60 , 62 are submerged in hydraulic fluid. The fluid fills the space behind plungers 274 and in the region of the spring 278 .
  • a close sliding fit is provided between plunger 274 and its associated bore with a slight space therebetween.
  • the diameter of the bore may be approximately 0.250 inch (plus or minus 0.0005 inch) and the diameter of the plunger may be 0.248 inch (plus 0.001 and minus 0.000 inch).
  • the hydraulic fluid, or oil, used in such exemplary system is Unocal Unax AW Grade 46.
  • a pair of electrically actuated solenoid valves 48 , 50 are secured atop manifold block 36 .
  • Solenoid valve 48 overlies bores 156 , 158 , 160 and solenoid valve 50 overlies bores 162 , 164 , 166 .
  • Solenoid valve adapters indicated generally at 294 , 296 are interposed between their associated solenoid valves and the underlying manifold block. Each of the solenoids and its underlying adapter is substantially the same, and thus only one set will be described in detail.
  • Solenoid control valves 48 , 50 are substantially similar. As best seen in FIG. 12, solenoid control valve 48 is positioned to control the flow of fluid between bore 158 and bores 156 , 160 adjacent thereto. Similarly, solenoid control valve 50 is positioned to control the flow of fluid between bore 164 and bores 162 , 166 adjacent thereto. Each solenoid control valve is associated with a base adapter 294 , 296 , respectively. When the adapter is screwed into one of the threaded bores 158 , 164 , a second orifice in the adapter will be aligned with an adjacent bore.
  • a solenoid control valve includes a spring-biased plunger which is normally closed, or seated, against the top of a bore in its associated adapter to prevent flow of fluid therethrough. Upon actuation of the solenoid the plunger is lifted to permit fluid flow.
  • adapter 294 comprises a unitary, or monolithic, body having a threaded lower protrusion 298 adapted to be screwed into the threaded upper end of its associated bore 158 .
  • a central bore 300 extends vertically through the adapter opening in the center of protrusion 298 and into the center of an internally threaded solenoid receiving cavity 302 .
  • a portion of bore 300 such as that shown at 300 a , may be selectively sized to control fluid flow rates therethrough. Bore 300 and portion 300 a should be larger in cross-section than orifice 262 in the flow rate control valve assemblies 54 , 56 . This allows valve assemblies 54 , 56 to perform their intended function, which they may not do if orifices 300 , 300 a are smaller.
  • a circumferential channel 304 extends about the underside of body 294 and is positioned to overlie the upper ends of both of bores 156 , 160 in body 36 .
  • An inclined, or side, bore 306 connects channel 304 with cavity 302 in a region offset to one side of the upper end of bore 300 .
  • two additional smaller annular channels 310 , 312 are concentric with channel 304 and receive O-rings 314 , 316 , respectively, to provide a seal between adapter 294 and base 36 .
  • Solenoid 48 is shown secured in the top of adapter 294 by being screwed into threaded cavity 302 .
  • a vertically shiftable plunger 320 is controlled by operation of the solenoid. Plunger 320 is shiftable between its normally-closed position as illustrated in FIG. 17 which closes off the top of bore 300 .
  • Upon actuation of the solenoid plunger 320 is raised from the top of bore 300 to permit fluid communication between bore 300 and inclined bores 302 , 306 . It should be recognized that bores 156 , 160 are constantly in communication with each other through annular channel 304 .
  • a chair as illustrated in FIG. 1 initially may be in its lowered and substantially upright position illustrated in dashed outline at 10 a .
  • its lift cylinder 22 is retracted and tilt cylinder 24 is extended.
  • the operator presses the “Up” button on the touch pad 86 which provides a signal to the circuit board 88 causing motor 38 to turn in the proper direction to actuate pump 42 to provide fluid under pressure to lift cylinder 22 .
  • Fluid is drawn from sump 44 , through check valve 64 , through pump 42 , through check valve 70 , past accumulator 76 , and through flow rate control valve 56 and another filter 84 to the lower end of cylinder, or ram, 22 to cause the chair to rise.
  • Accumulator 76 moderates the flow of pressure fluid both at starting and stopping of cylinder movement. With the flow rate valve 56 disposed in the fluid supply circuit between the accumulator and actuator 22 , valve 56 and the accumulator work together to moderate any fluid pressure surges. Explaining further, should an initial fluid pressure surge be produced by pump 42 such will be somewhat blocked by the restricted orifice of valve 56 permitting time for accumulator 76 to absorb the pressure surge.
  • the chair as raised is shown in solid outline in FIG. 1 .
  • fluid flow moderation is provided mainly by the flow rate control valve and the cushion valve.
  • fluid flow rate moderation at the end of movement is provided mainly by joint action of the accumulator and flow rate control valve.
  • FIGS. 13-17 operative elements for control of fluid supply and return to the lift cylinder 22 are shown in their at rest position, neither extending nor retracting cylinder 22 .
  • such assemblies relate to check valve 64 (FIG. 15) which is closed, check valve 70 (closed in FIG. 13 ), accumulator 76 and its pressure relief valve 80 (FIG. 13 ), flow rate control valve 56 (FIG. 16 ), and cushion valve 62 (FIG. 14 ).
  • the actual position of the piston body 234 may be retracted somewhat dependent upon the position of the chair and thus the pressure of fluid imposed upon the piston body.
  • pressurized fluid As pressurized fluid enters bore 132 on the pressure side of piston 234 of accumulator 74 , it causes the piston to move rearwardly into what may be considered to be a lower pressure side of the piston against the yieldable biasing force of spring 239 . This moderates the initial rush of pressurized fluid moving toward tilt ram 24 .
  • bore 132 on the lower pressure side of piston 234 (the side of spring 239 ) normally is filled with fluid, a portion of such fluid wall be forced from bore 132 , through bore 170 to return to the sump.
  • Pressure relief valve 82 also is capable of release to allow pressurized fluid to move therethrough to flow from the pressure side of the accumulator piston body to the lower pressure side of the piston and to drain therefrom through bore 170 back into the sump, if the pressure of the fluid supplied is greater than that to be controlled by the pressure relief valve 82 .
  • Fluid moving past the accumulator enters bore 154 (as seen in FIGS. 13 and 16) to flow rate control valve 54 .
  • the fluid flows through side port, or bore, 268 through orifice 262 in spool 260 and continues therefrom toward the tilt ram 24 .
  • fluid rate control valve 54 When fluid is flowing toward the tilt ram, fluid rate control valve 54 would be in the position as illustrated for valve 56 in FIG. 16 .
  • Port, or bore, 268 would be substantially clear for fluid to flow therethrough and the rate of fluid flow would be controlled solely by the size of orifice 262 in the end of spool 260 .
  • the moderating action of the accumulator and flow rate control valve produces a comfortable rate of tilt for a user of the chair.
  • motor 38 and pump 42 are operated in such a direction that fluid is drawn upwardly from sump 44 through ball check valve 64 , into horizontally disposed bore 136 , and down through bore 148 into kidney-shaped opening 120 .
  • Fluid thus delivered to the gear pump is pumped under pressure through kidney-shaped opening 122 to bore 150 and into horizontally disposed bore 138 .
  • this accumulator piston may shift longitudinally of bore 142 under the influence of fluid pressure against one side of its head and spring 238 and fluid in bore 142 on its opposite side to moderate fluid pressure surges. Fluid then travels from bore 142 into vertical bore 168 , through flow rate control valve 56 , and to the lift cylinder.
  • the valves and valve assemblies in the circuit supplying fluid to the lift ram operate similarly to those described for the circuit supplying the tilt cylinder.
  • solenoid control valve 48 is opened, by raising plunger 320 (see FIG. 17 ). This permits fluid to flow from the tilt cylinder 24 to cause the ram 24 to retract. Fluid under pressure flows initially into flow rate control valve 54 . The initial rush of higher pressure fluid is such as to impact upon the head of spool 260 and urge it to move downwardly as illustrated in FIG. 16 against the yieldable urging force of spring 264 . The lower end of the spool partially covers side bore 268 to add additional control for the rate of fluid flow through this valve.
  • spool 260 After the initial rush of fluid, spool 260 will reach a stabilized condition within sleeve 256 such that fluid will flow at a controlled rate outwardly therefrom to accumulator bore 132 where additional moderating will occur of the fluid pressure and flow.
  • fluid captured in the region of spring 278 behind the plunger seeps outwardly around the periphery of the plunger to exit through fluid return bore 170 which leads to the sump. Due to the length of plunger stroke as well as the close fit between the plunger and bore wall only a limited rate of fluid seepage occurs past the plunger so that the start of retraction of the ram is cushioned. Eventually sufficient fluid will seep from the region behind plunger 274 that it reaches the position illustrated for the plunger at the right side of FIG. 14 which exposes a larger portion of bore 170 for the flow of fluid from bore 134 .
  • the apparatus disclosed herein and its method of operation provide many advantages over prior systems.
  • the system is simplified both in the hydraulic control circuit and the electrical control circuit to provide both lifting and tilting for the chair.
  • the crescent gear drive pump higher pressure capabilities are obtained with a smoother and quieter flow and operation.
  • the gears are formed in involute profiles which do not require tight tolerances.
  • 14 pinion teeth and 19 driven teeth may be provided for smooth and quiet operation.
  • the monolithic manifold with a number of intersecting bores machined therein extending inwardly from external surfaces of the block, but not extending fully therethrough, with a plurality of valve and control assemblies received in the bores and closing plugs with seals, provides a compact efficient system which minimizes possibilities of leakage. Further, it provides a system which has a small external configuration making it more compact for use in selected systems.
  • the accumulators disclosed are inexpensive and simple to manufacture and operate. Since the rear side of each accumulator piston is connected to the sump the spring and piston may be bathed in oil for lubrication purposes and any small leakage across the piston seal will not greatly affect assembly performance. Further, since the entire accumulator assembly is incorporated into the base, or manifold, no external hoses or connectors are needed for the accumulators.
  • Pressure compensated flow rate controls which are self-actuating, provide restrictions so that the accumulator valves function properly and can compensate for a load so that the cylinders may retract at the same general speed regardless of the load on the chair. They provide a pressure drop so the accumulators may work for a wide variety of patient loads.
  • pressure relief valves in the accumulator pistons an inexpensive method is achieved for providing a relief path for hydraulic fluid in the event of overpressurization. Addition of such pressure limiting devices allows the omission of limit switches which normally would shut off a pump at full cylinder extension.
  • Timers are provided on the circuit board to limit the time that the pump operates. Further, similar time restraints are placed on the solenoids to limit the amount of time in which they are open or producing return action of the rams.
  • the inlet check valve assemblies are simple and inexpensive ways to accomplish the need for sealing in one direction and minimal pressure drop free flow in the other direction.
  • Particularly of interest are the O-rings in the check valves at the base of the unit which are improvements over hard seat-type valves which may be inclined to leak.
  • the O-rings provided supply a soft seal which produces generally trouble-free sealing.
  • the solenoid adapter base providing a circular path for oil between spaced apart bores not only provides a convenient method for providing desired fluid paths, but also may be supplied with different sized orifices and solenoid mounts so that different applications may be achieved.
  • the cushion valves provide smooth start of the lowering or return tilt action. They provide a smooth, slow chair movement at first and then allow more rapid movement through intermediate actuation.
  • the design of the monolithic base, or manifold is such that there are a minimal number of plugged bores and the stacking of parts on a machining center for producing such may be optimized. Also, combining these parts into the pump assembly minimizes costs, reduces potential leak points, and minimizes the volume of the assembly for convenient installation and use. Further, minimization of the height of the assembly allows the chair to move lower than would be permitted with earlier units.
  • kidney-shaped openings machined into the manifold, or base they may be precisely located with respect to the gears in the gear pump. This assists in providing quiet and smooth operation.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • General Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Animal Behavior & Ethology (AREA)
  • Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Chairs Characterized By Structure (AREA)
  • Accommodation For Nursing Or Treatment Tables (AREA)
  • Chair Legs, Seat Parts, And Backrests (AREA)
  • Control Of The Air-Fuel Ratio Of Carburetors (AREA)
US10/121,266 2001-04-12 2002-04-11 Hydraulic drive system Expired - Lifetime US6814409B2 (en)

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US10/121,266 US6814409B2 (en) 2001-04-12 2002-04-11 Hydraulic drive system
JP2002265383A JP4172974B2 (ja) 2002-04-11 2002-09-11 椅子用流体制御システム
AT02020775T ATE423912T1 (de) 2002-04-11 2002-09-16 Steuersystem eines stuhls
DE60231287T DE60231287D1 (de) 2002-04-11 2002-09-16 Steuersystem eines Stuhls
EP02020775A EP1353076B1 (de) 2002-04-11 2002-09-16 Steuersystem eines Stuhls
JP2008113022A JP5129643B2 (ja) 2002-04-11 2008-04-23 椅子用流体制御システム

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USD613532S1 (en) 2009-01-26 2010-04-13 A-Dec, Inc. Dental chair
USD613530S1 (en) 2009-01-26 2010-04-13 A-Dec, Inc. Dental chair base
USD613533S1 (en) 2009-02-02 2010-04-13 A-Dec, Inc. Dental chair
USD614422S1 (en) 2009-01-26 2010-04-27 A-Dec, Inc. Dental chair
USD614424S1 (en) 2009-01-26 2010-04-27 A-Dec, Inc. Portion of a dental chair with armrests
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USD630872S1 (en) 2009-01-26 2011-01-18 A-Dec, Inc. Dental chair back
USD624767S1 (en) 2009-01-26 2010-10-05 A-Dec, Inc. Dental chair
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USD614422S1 (en) 2009-01-26 2010-04-27 A-Dec, Inc. Dental chair
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US20100205742A1 (en) * 2009-02-13 2010-08-19 A-Dec, Inc. Patient support apparatus with neck support member
US20100207432A1 (en) * 2009-02-13 2010-08-19 A-Dec, Inc. Base and support system for a patient support apparatus
US8061664B2 (en) 2009-02-13 2011-11-22 A-Dec, Inc. Base and support system for a patient support apparatus
US8297564B2 (en) 2009-02-13 2012-10-30 A-Dec, Inc. Fluid control system for use with a patient support apparatus
US20160010669A1 (en) * 2013-03-28 2016-01-14 Mitsubishi Hitachi Power Systems, Ltd. Hydraulic device and prime mover device
US9797418B2 (en) * 2013-03-28 2017-10-24 Mitsubishi Hitachi Power Systems, Ltd. Hydraulic device and prime mover device
US11369539B2 (en) * 2019-05-13 2022-06-28 David J. Ahearn Dental chair
US11730655B2 (en) 2019-05-13 2023-08-22 David J. Ahearn Dental chair

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DE60231287D1 (de) 2009-04-09
US20020149248A1 (en) 2002-10-17
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JP5129643B2 (ja) 2013-01-30
EP1353076A3 (de) 2006-09-13

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